Análise microestrutural da hidratação do cimento Portland com águas residuárias provenientes de estações de tratamento de esgoto predominantemente doméstico

Abstract

The stricter criteria for discharging effluents into water bodies and the rising cost of water have encouraged reuse in industries, seeking to minimize conflict by using it more intensely in the arid and semi-arid regions of the globe. Civil construction has been increasing measures that minimize the impacts of its action on the environment, practicing the "sustainable construction", even for the production activities (kneading) and curing of concrete. Researchers state that for each m³ of concrete produced, approximately 1.13 m³ of water is consumed, 28% of this value with kneading. Thus, in this adverse scenario for local development, and in face of worldwide practices, studies and standards, the macro and microstructural analysis of concrete produced with 2 different types of Portland cement (CP III and CP V) were developed combined with 3 types of water (being potable, secondary treated effluent and tertiary treated effluent), where the large and fine aggregates were the same. For macrostructural analysis, normative evaluation techniques were used for kneading waters (such as physicochemical analysis) and paste analysis (handling times and normal consistency paste) as well as concrete (axial compressive strength, carbonation and abatement resistance). of the cone trunk). For the microstructural analysis of the paste, hydration heat (calorimetry), X-ray diffraction and thermoanalysis (thermogravimetry and differential exploratory calorimetry) techniques were performed for ages 1, 7, 14 and 28 days. Lyophilization technique was used to stop the hydration of the paste at the mentioned ages. In addition, and not least, microbiological analysis techniques (heterotrophic and coliform bacteria) were performed in the constituent waters and cements, as well as paste until 45 minutes of reaction. Some bacteria were also isolated and their behavior was evaluated when cement was added. The macrostructural results are encouraging, where predominantly there was no significant difference between the groups evaluated with distilled water, water standart reference. As for the microstructural analyzes, thermo-analyzes (calorimetry) performed there is no significant difference considering the sample deviation of the masses of calcium hydroxide and calcium carbonate (hydration temperatures up to 7 days). For the microbial analysis of paste, special attention is given to the sporulation capacity of bacteria, which is a future target to be investigated, since studies show that not all bacteria that sporulate are micro structurally harmful to cementitious materials.